As pointed out by previous posters a very difficult proposition. Consider this: A B737-400 Type III o/wing emergency exit which is a plug type, has an area of roughly 0.5 sq M. or 775 sq in. At a 2psi differential (less than 1/4 of max diff on the -400) the force on the exit is over 1500 lbs or 680 kg. The Pax entry door has an area of over 1.5 sq M and even with the mechanical advantage of the handle and mechanism requires around 20kg to "unlock" when unpressurised. Ever watched the struggle some of the cabin crew have opening a "classic '37" pax door? ps. I think I have the maths right.
Cheers,30/30